The influence of current direction on the Cu-Ni cross-interaction in the Cu/Sn/Ni joint configuration was investigated in this study. During current stressing, an electric current towards or away from the Ni-side of Cu/Sn/Ni was imposed at 150°C. It was observed that the (Cu,Ni) 6 Sn 5 ternary compound was the dominant reaction product at both interfaces, and its growth at the Ni-side strongly depended upon the direction and magnitude of the electron flow. When the electron flow was towards the Ni-side, more Cu was found to be driven to the Ni-side, resulting in an increase in the thickness of (Cu,Ni) 6 Sn 5 . This is due to the chemical-potential-induced Cu flux (J Cu chem ) that was enhanced by the electromigration (J Cu em ). In the case of electron flow away from the Ni-side, the supply of Cu to the Ni-side was retarded due to the fact that J Cu em was in the opposite direction to J Cu chem : The results of this study revealed that the Ni-side (Cu,Ni) 6 Sn 5 thickness remained almost unchanged under current stressing of 10 4 A/cm 2 at 150°C, which suggests the inward Cu flux is approximately equal to the outward flux, i.e., J Cu chem % J Cu em :